Method of controlling weather

ABSTRACT

A pyrotechnic formulation for use in weather modification comprising a fuel and an oxidizer and a mixture of a metal iodate and an alkali iodate. Upon combustion metal iodide and alkali iodide are generated as mixtures and complexes which show ice nuclei activity at from -5* to -20* C. depending on the molar range of metal iodide to alkali iodide.

United States Patent 11 1 [1 1 3,915,379 Burkardt et a1. Oct. 28, 1975METHOD OF CONTROLLING WEATHER 2,550,324 4/1951 Brandau 239/2 R [75]Inventors: Lohr A. Burkardt; William G. 2995526 8/1961 DeMent 3,046,1687/1962 Burkardt et al 149/87 X Ffnnegan; Frederlck Odencramz; 3,127,1073/1964 Merriweather 239/2 R St-Amand; Charles 11 3,375,148 3/1968Finnegan et a1.

Stanifer, all of China Lake, Calif. 3,418,184 12/1968 Vetter 3,545,67712/1970 Power 239/2 R [73] Assignee: The United States of America asrepresented by the Secretary of the Navy, Washington, DC, PrimaryExaminerBenjamin R. Padgett Assistant ExaminerE. A. Miller [22] Flled:1971 Attorney, Agent, or FirmR. S. Sciascia; Roy Miller;

[21] Appl. No.2 126,879 Lloyd E. K. Pohl I Related US. Application Data[62] Division of Ser. No. 767,068, Oct. 10, 1968, Pat. N0. ABSTRACT Apyrotechnic formulation for use in weather modlfi- [52] Cl 239/2 Rcation comprising a fuel and an oxidizer and a mixture [51] Int. Cl 213/00 of a metal iodate and an alkali iodate. Upon combus [58] Field239/2 149/l9 2O 81 tion metal iodide and alkali iodide are generated asg mixtures and complexes which show ice nuclei activity [56] ReferencesCited at from to 20 C. depending on the molar range UNITED STATESPATENTS of metal 1od1de to alkali 1od1de.

2,527,231 /1950 Vonnequt ..239/2RX 2Claims,3Drawing Figures Ill-I E Q Em d 3 1:1 z 2 in 2 g MOLE 11/1110 u. AUI Kl O c c 9 3 1 A O 1 1 g 12 m 10 2 0 1 3 g A 1 12 A 1 9 STD TEMPERATURE, C

US. Patent 01x28, 1975 Sheet 1 of2 3,915,379

MOLE RATIU Agl TEMPERATURE, c

Fig.

METHOD OF CONTROLLING WEATHER GOVERNMENT INTEREST The invention hereindescribed may be manufactured and used by or for the Government of theUnited States of America for governmental purposes without the paymentof any royalties thereon or therefor.

BACKGROUND OF THE INVENTION This invention is a division of patentapplication Ser.

No. 767,068, filed Oct. 10, 1968 now US. Pat. No. 3,802,971.

Weather modification has been applied in different parts of the worldand several methods and means have been used to modify the physical anddynamical conditions of the atmosphere. Particles exist in theatmosphere which have the ability to form ice crystals in supercooledclouds. These are called natural or atmospheric ice nuclei and areresponsible primarily for most of the natural ice formation in the cloudand their absence is strongly related to the supercooling of the cloud.When a supercooled cloud is seeded with ice nuclei, ice crystals areformed which start growing by abstracting water vapor from thesurrounding atmosphere or by freezing the cloud droplets by accretion.There are two widely used artificial ice nuclei: dry ice (solid carbondioxide) used successfully for cloud modification by Schaefer in 1946,and silver iodide whose excellent activity was discovered by Vonnegut in1947. Re- 30 ical and physical properties. The generation of pure sil- 35 ver iodide has been studied in the past to characterize the generationprocess and to establish ice nuclei characteristics as a function ofsilver iodate concentration in the pyrotechnic. The present inventionprovides a number of new pyrotechnic compositions which upon 40combustion show ice nuclei activity at from 5 to C. and provide moreeffective cloud seeding.

SUMMARY OF THE INVENTION This invention is for improved pyrotechniccompositions. The compositions comprise a fuel and oxidizer mixture towhich a mixture consisting of a metal iodate and an alkali iodate isadded. The products of decomposition are the metal iodide-alkali iodidein varying molar ratios, complexes and other mixtures which induce thefreezing of supercooled water droplets in cold clouds and fogs in aneffective manner.

The general object of this invention is to provide a composition whichupon combustion yields freezing nuclei having greatly increasedactivity, especially at the higher temperatures approaching 0 C. Anotherobject is to provide pyrotechnic compositions which are inexpensive toformulate and are simple to use in dispelling fog, suppressing hailformation and increasing rainfall.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows nuclei activity of thepotassium iodidesilver iodide complex wherein the mole ratio of AgI-Klranges from 3:1 to 1:65;

FIG. 2 shows the ice nuclei activity for the initial series offormulations (Examples 4, 5, 7, 8, and 9) wherein silver iodide is shownas the working standard; and

FIG. 3 shows the nuclei activity of the lithium iodidesilver iodidecomplex.

DESCRIPTION OF THE INVENTION In accordance with the present inventionformulations comprising a fuel, an oxidizer, a metal iodate selectedfrom the group consisting of silver, lead, copper, and bismuth iodatesand an alkali iodate selected from the group consisting of lithium,sodium, potassium, rubidium, cesium and ammonium iodates were blended.The formulations were then pressed, cast, or extruded into the desiredshape and cured.

The following examples set forth in Table I will better illustrate theinvention but should not be considered as limiting thereof.

TABLE I Pyrotechnic Compositions (Ingredients by Weight) NucleationSample Metal Iodate Alkali lodate Oxidizer Fuel Temp. C.

1 AglO 5% NH IO 5% NH NO Nitrosol 50% 2 PbIO 5% NH IO 5% NH NO 40%Nitrosol 50% 3 Aglo 15% NaIO 28.73% NH NO 6.27% PNC 50% 4 AgIO; 15% NaIO15% NH NO 20% PNC 50% 5 AgIO, 5% U10; 5% NH.NO; 40% PNC 50% 6 AgIO 5%NaIO; 5.44% NH NO 39.56% PNC 50% 7 AglO 5% K10: 5.88% NH NO 39.12% PNC50% 8 AglO 5% CslO 8.46% NH NO 36.54% PNC 50% 9 AgIO; 5% RbIO 7.16% NHNO 37.84% PNC 50% 10 AglO 5% C510; 1% NH N0 44% PNC 50% 11 AglO; 5% RbIO1% NH NO 44% PNC 50% 12 Pb(.10;,) 5% LilO 5% NH,NO 40% PNC 50% 13 AglO5% NalO 1% NH NO 44% PNC 50% I4 AglO 5% K10 1% l\11-1.,NO 44% PNC 50% 15AglO 5% M10: 1% NH NO 44% PNC 50% 16 AgIO 5% U10: 1% NH No 44.9% PNC 50%17 AgIO; 5% K1O 0.1% NH NO; 44.9% PNC i 50% 18 AglO; 5% CslO 0. 1% NH NO44.9% PNC 50% 19 AglO 5% K10;, PNC

20 AgIO 5% K10: 1.26% NH N0 43.74% 50% PNC 21 AglO 5% K10: 1.89% NH N043.11% PNC 50% 22 AgIO 5% KID 3.79% NH,NO 41.21% PNC 50% 23 AglO 5% K10;7.58% NH NO 37.42% PNC 50% 24 AglO; 5% KIO 11.35% NH NO 33.65% PNC 50%25 AglO 1% K10; 49% PNC 50% TABLE I-Continued Pyrotechnic Compositions(lngredients by Weight) Nucleation Sample Metal lodate Alkali lodateOxidizer Fuel Temp. C.

26 AglO; 5% K10: 5.88% NH NO 34.12% PNC 50% Al 5% 27 AglO 1% LilO; 10%PNC 50% K10 39% 28 AglO 5% K10;, 5.88% NH N 34.12% Al PETRlN 15% PNC 35%29 AglO; 1% NalO 49% PNC 50% 3O AglO 5% N310; 1.17% NH NO: 43.88% PNC50% 31 AglO 5% NalO; 3.5% NH.NO; 41.5% PNC 50% 32 AglO 5% NalO, 10.5% NHNO 34.5% PNC 50% 33 AglO; 12.04% LilO 1.36% NH NO 36.6% Nitrosol 50% 34Pb(lO;l)2 K10 11.75% NH NO 28.25% PNC 50% 1.8 35 Pb(lO;,) 10% K10 8% NHNO 32% PNC 50% 3.2 36 Pb(1O 10% K10; NH NO; PNC 50% 1.2 37 Pb(1O 10% K1019.4% NH NO 20.6% PNC 50% 1.5 38 Pb(lO;) 10% LilO 6.5% NH NO, 33.5% PNC50% 3.2 39 Pb(lO 10% U10 10% NH NO PNC 50% l.5 40 P1)(10:)z 10% LilO:13% NH NO;, 27% PNC 50% l.0 41 P1I(1 :i)z 10% K10 1.92% NH NO 38.08% PNC50% 2.0 42 Pb(lO 10% K10 1.28% NH.NO;, 38.72% PNC 50% 1.2 43 Ph(10; 10%NalO 1.77% NH NO; 38.23% PNC 50% -O.8 44 Pb(10;,) 10% NaIO 3.55% NH NO36.45% PNC 50% 1.0 45 Pb(10;,) 10% NalO 7.06% NH NO 32.94% PNC 1.0 46AglO 10% K10 15.14% NH NO 24.36% PNC 50% -l.0 47 AglO: 10% 1410;, 22.70%Nl-LNO 17.30% PNC 50% 1.0 48 AglO 10% K10; 30.27% Nl-LNO; 9.73% PNC 50%0.8 49 CulO 10% NH NO 40% PNC 50% 50 CulO 10% 1(10 10.35% NH NO 29.65%PNC 50% 51 CulO 10% K10 15.53% Nl-LNO; 24.47% PNC 50% 52 CulO 10% K10;20.71% NH NO; 19.29% PNC 50% 53 Cu(1O; 10% Lilo; 8.80% Nl-LNO; 31.2% PNC50% 54 Cu(1O;) 10% LilO 13.20% NH,NO; 26.80% PNC 50% 55 Pb(103)z 10% K1026.89% NH NO; 13.11% PNC 50% 1 56 Pb(l0;,) 10% K10; 30.74% NH NO 9.26%PNC 50% 1 57 Pb(10; 10% K10 43.58% NH NO; 5.42% PNC 50% 0.5 58 131(103);10% L110;, 7.43% NH,N0= 32.57% PNC 50% 59 PbCO 3% K10 7% NH NO; 40% PNC50% Pb(OH) 60 Bi(lO 10% NalO 8.09% NH NO 31.91% PNC 50% 61 Bi(lO 10% K108.75% Nl-LNO 31.25% PNC 50% 62 Pb(1O;,) 10% NH NO 40% PNC 50% 63 AglO10% NH NO 40% PNC 50% AglO; silver iodate Pb(10=) lead iodate Cu(lOcopper iodate Bi(lO bismuth iodate X10; potassium iodate NalO sodiumiodate LilO lithium iodate CalO cesium iodate RblO rubidium iodate NH NOammonium nitrate PNC plastisol nitrocellulose Nitrosol comprises about30% plastisol nitrocellulose and about pentaerythritol trinitrateExamples were first prepared incorporating silver iodate and lead iodatewith an alkali iodate in a nitrosol binder to which the additionaloxidizer, ammonium nitrate, was added to ensure proper combustion.Nitrosol comprises about 30% plastisol grade nitrocellulose (PNC) and70% pentaerythritol trinitrate (PETriN). Other nitrate esters such asnitroglycerin, metriol trinitate, triethylene glycol dinitrate, etc.,may be used. The ratio of plastisol nitrocellulose (PNC) to nitrateester varies with the particular lot of nitrocellulose and ester chosen.The formulations using nitrosol were easily 60 made by first preparingthe binder which comprises blending plastisol nitrocellulose and anitrate ester in a vacuum mixer at room temperature until a homogeneousbubble-free mixture is obtained. The desired amount of metal iodatealkali iodate and ammonium nitrate are added and vacuum mixing continueduntil a homogenous bubble-free mixture is obtained. The material is thencast into the desired form and oven cured.

50 The temperature and time of cure depends on the size and shape of thecasting. For example, a cylinder about 1 inch in diameter and 2 incheslong may be expected to cure in l to 2 hours at a temperature rangingfrom to F. The ratio of nitrosol to solid additives (metal iodate,alkali iodate, ammonium nitrate, aluminum) is determined by the oxygenbalance and the particle size of the solids. The particle size shouldresult in a mix viscosity which is castable but which will not permitthe solids to settle out.

The plastisol nitrocellulose (PNC) used herein is commerciallyavailable. It is a dense, spherical nitrocellulose of from 1 to 30p.median diameter and is not substantially attacked by the plasticizersuntil cure at elevated temperatures is initiated. Plastisolnitrocellulose is prepared by placing 90 grams of nitrocellulose (12.6%N), 1.2 grams of ethyl centralite and 1.4 liters of nitromethane in aflask and stirring vigorously until dissolution occurs, stirring slowlyfor an additional 10 minutes to insure homogeniety, adding to theresulting lacquer 19.2 grams of a petroleum sulfonate emulsifying agentfor nitrocellulose in about 900 ml of water and circulating through acollard mill for about minutes, draining the resulting emulsion from themill into about 30 liters of water and stirring about minutes until anitrocellulose precipitate is formed which is filtered from the liquid,washed in hexane, dried for about 16 hours and sifted through a 200 meshscreen.

The formulations shown in Table 1 above may be modified as necessary togenerate the desired complex nuclei. In place of the plastisolnitrocellulose double base formulations were used. They comprise about51% by weight nitrocellulose, 43% by weight nitroglycerin, and theremainder diethylphthalate, a plasticizer, and ethyl centralite, astabilizer. Cast double base comprising nitrocellulose and nitroglycerinin major amount petrin and metriol trinitrate in minor amount alsoprovided a good fuel for the metal iodate-alkali iodate mixture.

The products of combustion of these examples using nitrosol binder werecollected, characterized by wet chemical and X-ray diffration analysisand the results compared with data on known complexes. Ice nucleiactivity spectra were measured in a Naval Weapons Center cloud chamberburning small pyrotechnic samples directly in supercooled fog of 1 g/mliquid water content. These fogs evaporate in 3-8 minutes, dependent onoperating conditions if not nucleated. Each experiment utilized 100 mgof pyrotechnic containing 10% of the heavy metal derivative burned atone point in the chamber. Nucleation temperatures were taken as thosewhere complete icing of the chamber occurred, but do not necessarilyrepresent the true droplet equilibrium threshold values.

The activity spectra for the initial series of formulations werecompared with silver. iodide as a working standard (see FIG. 2). Thespectrum for complex cesium iodide-silver iodide nuclei did not showenhanced activity over that for silver iodide alone. Nevertheless,sufficient cesium iodide was present in the nuclei to complex the silveriodide completely. The rubidium iodide-silver iodide system showsslightly enhanced activity over that of standard silver iodide. Thesodium iodide-silver iodide, potassium iodide-silver iodide, and lithiumiodide-silver iodide nuclei all show greatly enhanced activity.

The potassium iodide-silver iodide series showed the highest activity atwarmer temperatures. Formulations calculated to yield complex nucleiwith potassium iodide-silver iodide ratios of 1:3, 2:1, 3:1, 12:1, and65:1 are shown in FIG. 1. The 3K1 Agl complex shows the highestactivity. Although less effective at warmer temperatures, the 65K] Aglnuclei show excellent activities at lower temperatures.

Nuclei having a molar ratio of 651(1 to one Agl (97.87 wt. K1, 213 st.Agl) are completely soluble when sufficient water is acquired to yield acomposition of 39 wt. water and 61 wt. of the nuclei material.

The LiI-2Agl complex follows the behavior of the K1- Agl complex shownin FIG. 3.

Table 11 gives the nucleation temperature values obtained for silveriodide and several complexes of silver iodide and potassium iodide.

TABLE II Pyrotechnic Nucleation Composition Temp., C.

AglO 0 AglO .2 K10 l.0 AgIO .3 K10 l.0 AglO .4 KIO -0.8

Table III shows the temperature of nucleation of the decompositionproduct of lead iodate and those if its complexes with several alkaliiodides.

TABLE III Ice Nucleation Temperatures Table IV shows the values obtainedfor nuclei generated by combustion or pyrotechnics containing cupriciodate alone and with added alkali iodates.

TABLE IV Ice Nucleation Temperatures lllll Bi( 109 .3 LiIO, Bi( [09 .3KIO The unexpectedly high threshold temperature values obtained suggeststrongly that contact freezing of droplets is the major mechanism of icecrystal formation.

Under the test conditions of an evaporating fog, silver iodide canfunction as an ice nuclei at measured air temperatures of +0.5 C.

Tentative interpretation of the data in Tables II-V suggests thefollowing:

Heavy metal iodides are more effective nuclei than the correspondingoxides. Molybdenum and bismuth iodides are thermodynamically unstableand are not formed during combustion processes. Complexes of the oxideswith alkali iodides are also not active at high temperatures. Lead andcopper iodates decompose to give oxyiodides of intermediate activity.Complexing with alkali iodides may enhance activity. Silver iodide showsthe highest temperature threshold and is a stable product of combustionof silver iodate. Complexes of silver iodide and alkali iodides areequally effective as ice nuclei.

The new compositions disclosed herein are pyrotechnics which aregenerally low explosives that have but little explosive value because oftheir low rates of combustion and the liberation of relatively littlegas per unit weight of composition. The combustion by products of thepresent compositions include the silver iodidealkali iodide complex,lead iodate and those of its complexes with several alkali iodides,cupric iodate alone and with alkali iodates, complexes of bismuth andmolybdenum oxides and alkali iodides. All of the samples are well withinthe safety requirements of a military pyrotechnic.

Metal such as aluminum is added to raise the flame temperature andadditional oxidizer (in addition to the iodates) is added to ensureproper combustion.

Many cloud seeding techniques have been used to introduce the metaliodide-alkali iodide complexes formed upon combustion of these newpyrotechnics into undercooled clouds whereby rainfall was attained andhail suppression was achieved. In several experiments the compositionwas ignited on a mountain top and the complexes entrained into the rangeof clouds to be seeded by updraft. The material was also ferrieddirectly into the clouds to be seeded by aircraft provided with specialdevices for expelling the pyrotechnics which produced the atomizedseeding material. Rockets and artillery missiles have also been loadedwith the composition and fired into the appropriate cloud.

These new pyrotechnic compositions either seed the cloud and producerainfall or snow if they reach the cold part of the cloud or theydissolve out. Most of the complexes formed upon combustion of thecomposition, e.g., Agl-KI, break down with water and silver or leadiodide, as the case may be, is precipitated out. All of the compositionsin the dry state nucleate ice but they must be dispersed into the cloudat the right temperatures (20 to C.). Most of them are quite effectiveif the complex is dropped into the clouds and overseeding the tops ofconnective clouds has stopped clouds from raining.

The herein described compositions must be brought into a state of finedispersion for the seeding of the clouds to successfully suppress hail,increase rainfall or disperse fog. The present invention providessubstances which show better capability of forming freezing nuclei assilver iodide alone, and are simple and inexpensive to prepare.

What is claimed is:

l. A method for artificially influencing the weather which comprisesoverseeding the tops of convective clouds with a silver iodide-potassiumiodide complex whereby rainfall is suppressed.

2. A method for influencing the weather comprising the steps of:

a. providing a pyrotechnic formulation containing the following:

said fuel binder being selected from the group consisting of: plastisolnitrocellulose, nitrosol, double base propellant binder consistingessentially of nitrocellulose and nitroglycerine, cast double baseconsisting essentially of nitrocellulose, petrin, metriol trinitrate,and the binder system consisting essentially of a carboxylated linearpolybutadiene having a carboxy end group present on both ends of thepolymer chain and tris [1-(2 methyl) aziridinyl] phosphine oxide andtrimethylol ethane trinitrate; said oxidizer being selected from thegroup consisting of ammonium iodate, ammonium nitrate, and ammoniumperchlorate; said metal iodate being selected from the group consistingof the iodates of copper, silver, lead, bismuth and molybdenum; and saidalkali iodate being selected from the group consisting of the iodates oflithium, sodium, potassium, rubidium, cesium and ammonium; b. formingthe pyrotechnic formulation into a desired shape and curing it; and c.burning the shaped and cured pyrotechnic formulation above a cloudhaving an air temperature in the range of from 20 to 0C to form complexmetal iodide-alkali iodide ice forming nuclei.

1. A METHOD FOR ARTIFICIALLY INFLUENCING THEM WEATHER WHICH COMPRISESOVERSEEDING THE TOPS OF CONVECTIVE CLOUDS WITH A SILVER IODIDE-POTASSIUMIODIDE COMPLEX WHEREBY RAINFALLS IS SUPPRESSED.
 2. A method forinfluencing the weather comprising the steps of: a. providing apyrotechnic formulation containing the following: